"Re-order tabs" crashes WordPress

Hi There,
On my website (http://eventlocations-baden.de)
I have Whoop installed and in the listing page I disabled all tabs except für “Profile/Profil”, “Info/Details” and “Map/Karte”.
See here: http://eventlocations-baden.de/eventlocations/rastatt/badnerhalle-rastatt/

The problem is, that “reviews” is the default active tab, but as it is hidden I get a weird view with “no” tab open.

So I tried changing the active Tab to “Profile” following this guide: https://wpgeodirectory.com/re-order-tabs-in-a-listing-detail-page/
I just copied all the code to the functions.php of the theme and changed that active tab within the code.

The result is as expected, but after a few page reloads I get a White Screen of Death, that can be fixed by deleting the whole Whoop Theme and then reinstalling it “clean” (without the functions.php modification).

Can somebody help me get my tabs right?? 🙂